1. Field of the Invention
The present invention relates to mounts for terminating optical fibers. More specifically, the present invention relates to mounts for terminating fiber optic catheters used for irradiating and ablating intravascular regions during surgical operations.
2. Description of the Related Art
Fiber optic catheters are hollow tubular devices containing optical fibers. Such catheters are inserted into veins or arteries to illuminate internal parts of the body for diagnostic and surgical purposes. Many medical applications require delivery of light energy, such as laser energy, through an optical fiber or similar waveguide device disposed in a body cavity for treatment or diagnosis. These include the ablation of tissue such as plaque and tumors, the destruction of calculi and the heating of bleeding vessels for coagulation. The lasers used may produce either pulsed or continuous-wave light of wavelengths ranging from the ultra-violet to the infra-red. In these applications, some way to couple the laser to the optical fibers of the catheter is required.
FIG. 1 depicts a perspective view of a fiber optic catheter employing a mount according to the present invention. As used herein, "proximal" refers to closer to the source of energy and "distal" refers to further from the source of energy. Thus, the distal end of the catheter is the end of the catheter which is to be inserted into a body cavity or lumen and the proximal end of the catheter is the end which remains outside the body. Similarly, the end of the fiber optic connector which receives the fiberoptic cable will be referred to as its distal end, and the opposite end of the connector, where the fibers are terminated, will be referred to as its proximal end. The fiberoptic connector described herein below will be referred to as a proximal mount because it is mounted to the proximal end of the cable. A proximal end 12 of light conveying cable 16 is connected to proximal mount 14. Strain relief 10 is disposed around light conveying cable 16 to protect the catheter from damages due to stresses along the assembly. Light conveying cable 16 has optical fibers disposed within, and these fibers are affixed to proximal mount 14 using techniques more fully described herein.
A second end of light conveying cable 16 is attached to a side branch 18 of bifurcating adaptor 20, and guide wire 22 is fed into an inline branch 24 of bifurcating adaptor 20. The other end of bifurcating adaptor 20 is attached to catheter 26, which has an outer body, an inner body disposed within the outer body to form an outer lumen therebetween and an inner lumen within said inner body, optical fibers disposed within the [space between the] outer lumen, and guide wire 22 running through the center of the catheter. The inner body and the outer body may be constructed from any of a number of suitable materials, such as plasticized vinyl resins, polyethylene, synthetic and natural rubbers and polyurethane elastomers. The distal end of catheter 26 is terminated by tip 28. Proximal mount 14 will now be described in detail.
FIG. 2 is an enlarged perspective view of a proximal mount for a fiber optic catheter according to the prior art. The proximal end 12 of light conveying cable 16 containing optical fibers 202 passes through strain relief 10 and into a distal side of mount body 204. Strain relief 10 may be of a coil or elastomer type material as is known in the art, and the mount body 204 may be made of any suitable material, such as aluminum or plastic, e.g., Delrin, PVC, polycarbonate, etc.
The light conveying cable 16 passes through mount body 204 and emerges from its proximal side. The optical fibers 202 extend past the terminal end of the light conveying cable casing 206 and spread out in a ribbon-like fashion to form a linear array of optical fibers 208. This array is bonded to a quartz slide 210 which has a distal end fixed to mount body 204. Bonding of fiber array 208 to quartz slide 210 may be done with any conventional adhesive, e.g., epoxy, cyanoacrylate, etc. Structural integrity may be increased by providing a bonding element 212 to bond on top of the fiber array 208 so that it is "sandwiched" between quartz slide 210 and element 212.
The terminal ends of the optical fibers 214 are substantially coterminal with the proximal end of quartz slide 210. The proximal end of the assembly is polished to provide a smooth optical surface. Cover 216 is attached to quartz slide 210 which covers the optical fiber assembly to protect it from damage. A portion of cover 216 has been "cut away" in FIG. 2 to more clearly show the structure of the mount; however, the cover actually extends over the entire fiber assembly and is substantially symmetric about a vertical plane passing through the center of the mount.
Mount body 204 may be provided with pins 218 and holes 220 to actuate switches associated with the light source to provide information to the laser concerning the nature of the catheter, such as its size and the power level to be delivered by the laser to the catheter. One such system is disclosed in U.S Pat. No. 4,919,508 to Grace et al., incorporated herein by reference.
In use, the proximal mount is mated with an appropriate receptacle of a light source such as a laser. The light energy from the source is directed onto the terminal ends 214 of fiber array 208. This energy is conveyed by the fibers through light conveying cable 16 to the distal tip of the catheter where it emerges, thus providing energy for ablation of intravascular regions and other operations as described above.
A quartz slide is used in the prior art design for several reasons. First, it was found that intense light energy (for instance, from a laser) hitting slides made from other materials tended to degrade the material quickly. This degradation generally left deposits of debris on the terminal ends of the fibers, thus decreasing the light transmitting capabilities of the catheter. Also, in the prior art design, the fibers are bonded directly to the slide and the bonding glue near the proximal end is burned off with a CO.sub.2 laser. A quartz slide is not damaged by this process as are some other types of slides. Finally, the operating environment of the proximal mount subjects the slide to a range of temperatures. The low coefficient of thermal expansion of the quartz slide reduces alignment problems as compared to other materials which may have greater coefficients of thermal expansion.